In the fabrication of integrated circuits on substrates, such as semiconductor wafers, the vapor deposition of chemicals, such as chemical vapor deposition (“CVD”) and more recently atomic layer deposition (ALD), is often desirable. The expansion of suitable source chemicals has increasingly led to use of precursor materials that are naturally liquid or solid at room temperature and atmospheric pressures.
In order to effectively deposit using precursors from a solid source material or chemical, a solid source material must, of course, first be vaporized. In pursuit of this goal, sublimation apparatuses are used to effectuate the vaporization of a solid source material. In addition, heat sources are often employed in conjunction with such an apparatus in order to increase the vapor pressure above the solid source material.
Unfortunately, existing semiconductor processing systems, of which a sublimation apparatus is a component, have a number of shortcomings including offering both an inadequate ratio of solid source surface area to vapor volume, and poor vapor/solid contact time. Often, current processing systems can allow carrier gas to flow from inlet to outlet without intimately contacting the solid source material, thus preventing the carrier gas from becoming saturated with solid source vapor. In addition, a conventional sublimation bed, which seeks to increase vapor/solid contact time, is often prone to “tunneling.” Tunneling results from the tendency of gas to flow preferentially along low resistance paths, rather than through the bulk of the powder, such that progressively smaller solid precursor surface area is exposed to the gas flow as the tunnel through the powder widens. It is thus progressively more difficult to saturate the carrier gas, even though the sublimation bed contains plenty of unvaporized solid source powder.
The present invention provides improved semiconductor processing systems. In the illustrated embodiments, the systems include a guidance structure, such as a support medium having a surface onto which a solid source for vapor reactant is coated. The illustrated guidance structures are configured to facilitate the repeated saturation of the carrier gas with the solid source for a vapor reactant.
In accordance with one aspect of the invention, a substrate processing system is provided with a source of a carrier gas, a support medium having a surface onto which a solid source for vapor reactant is coated and a reaction chamber located downstream of the support medium. The support medium is configured to guide the carrier gas, which originates from the carrier gas source, through the support medium.
In accordance with another aspect of the invention, a sublimation system is provided with a source of carrier gas and flowable support elements onto which a solid source for vapor reactant is coated. The support elements are configured to guide the carrier gas through the support medium in a generally non-linear contact path.
In accordance with yet another aspect of the invention, a sublimation apparatus comprises a sublimation vessel, a bed of a solid source for vapor reactant within the vessel, and a guidance structure configured to guide the carrier gas to contact the vapor reactant from the bed of the solid source material.
In accordance with a preferred embodiment, the guidance structure is configured to segregate and guide the carrier gas over the surface area of the solid bed by providing a winding contact pathway. Preferably, this path is also long and narrow. A vessel inlet port is located at the beginning of the contact pathway, while a vessel outlet port is located at the end of the contact pathway. The carrier gas guidance structure is configured to ensure contact of the carrier gas with the vapor reactant along a substantially segregated and winding contact pathway having a length greater than about 2.5 times a linear distance measured from the inlet port to the outlet port.
In accordance with other preferred embodiments, methods of processing a substrate and methods of performing an atomic layer deposition (ALD) process to deposit a layer on a substrate surface are provided. Preferably, these methods substantially saturate a carrier gas with precursor vapor. In certain preferred embodiments, a substantial plug flow of the carrier gas exits a sublimation vessel substantially saturated with precursor vapor by substantially exhibiting a plug flow residence time distribution by design within said vessel.
A feature of preferred embodiments of the present invention is that a precise and consistent quantity of reactant vapor can be delivered to a deposition chamber at high frequency. An additional feature of the preferred embodiments is an increased ratio of exposed solid source surface area to sublimation vessel volume as a result of, among other factors, the avoidance of problematic “tunneling.” Another feature of preferred embodiments is increased vapor/solid contact time. Yet another feature of preferred embodiments is the allowance of relatively even gas flow resistance over the life of a sublimation bed. Another feature of certain preferred embodiments is the production of a substantially plug flow residence time distribution of the carrier gas substantially saturated with precursor vapor.
These and other features are outlined in greater detail in the preferred embodiments described below.
For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described herein above. Of course, it is to be understood that not necessarily all such features, objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments having reference to the attached figures, the invention not being limited to any particular preferred embodiment(s) disclosed.